Revert "Fixing changes to make greentea test mbed-os-tests-netsocket-connectivity pass for target Realtek AMEBA"

This reverts commit 1fcfced.

Author: prashantrar

features/FEATURE_LWIP/lwip-interface/lwip_stack.c

@@ -594,13 +594,11 @@ nsapi_error_t mbed_lwip_emac_init(emac_interface_t *emac)
 // Backwards compatibility with people using DEVICE_EMAC
 nsapi_error_t mbed_lwip_init(emac_interface_t *emac)
 {
-    nsapi_error_t ret = NSAPI_ERROR_OK;
+    nsapi_error_t ret;
     mbed_lwip_core_init();
-    if(netif_inited == false){
-        ret = mbed_lwip_emac_init(emac);
-        if (ret == NSAPI_ERROR_OK) {
-            netif_inited = true;
-        }
+    ret = mbed_lwip_emac_init(emac);
+    if (ret == NSAPI_ERROR_OK) {
+        netif_inited = true;
     }
     return ret;
 }

targets/TARGET_Realtek/TARGET_AMEBA/RTWInterface.cpp

@@ -247,9 +247,8 @@ nsapi_error_t RTWInterface::connect(const char *ssid, const char *pass,
 nsapi_error_t RTWInterface::disconnect()
 {
     char essid[33];
-	
+
     wlan_emac_link_change(false);
-	mbed_lwip_bringdown();
     if(wifi_is_connected_to_ap() != RTW_SUCCESS)
         return NSAPI_ERROR_NO_CONNECTION;
     if(wifi_disconnect()<0){